In this project we have been studying developmental adaptations of T. cruzi to the vertebrate host and, in particular, the molecular basis of adaptive changes occurring during the differentiation of epimastigotes (vector stare) to metacyclic tryptomastigotes (infective stage). This year we succeeded in cloning a previously characterized developmentally regulated molecule from the parasite which has decay accelerating factor (DAF) activity inhibiting parasite mediated complement activation. The molecule has extensive sequence homology with human DAF.